Selective signaling system



May 12, 1936. R. BQWN SELECTIVE SIGNALING SYSTEM Filed May 26, 1954 2 Sheets-Sheet l Y @EN MANN@ R. 50m/L BY ArroRm-:v

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May l2, 1936. R. BQWN 2,040,462

SLECTIVE S IGNALING SYSTEM |IIHIIIII Trans.

2 Car/'IbrlNvENToR 4 Zlown "Y fkk?. ATTORNEY Patented May 12, 1936 UNITED STATES lPATENT OFFICE l' z,o4o,4sz I sELEc'rlvl-z sIGNAuNG srs'rEM Ralph' Bown, Maplewood, N. J., assignor to American Telephone and Telegraph Company,

a corporation of New York Y Application May 26, 1934, Serial No. 727,801

13 Claims.

This invention relates to high-frequency transmission systems employing radiated waves or waves directed by wave guides and to the control of apparatus by pulses or selective signals sent from one station to another in such systems. More particularly it relates to arrangements for selec- 'tively calling one or more stations from a control station while holding all other stations inoperative.

In high-frequency communication systems characterized by groups of stations intercommunicating by a common medium or by frequencies used in common, the communication of one station to another station may be heard at all stations, and any station may break into the communication by operating its transmitter. One object of the present invention is to provide means whereby such overhearing or interruption may be prevented.

In accordance with this invention, circuit arrangements are provided whereby the carrier frequency and/or code signals superimposed thereon, emanating from one station, may operate a. call signal at a desired station or stations, leaving apparatus at such stations in operative condition, and may render the apparatus at all other wherein another way of transmitting code signals is illustrated.

Fig. 4 illustrating application of the invention I to a network of stations.

In Figs. l, 2, and 3 the left portion of the figures illustrates a control station adapted to control and communicate with a number of secondary or controlled stations, of which for simplicity but one is illustrated at the right hand of the figures.

Referring to Fig. 1, the high-frequency transmitter I, which may be a radio transmitter and which may be associated with a receiver 36 for two-way communication, is supplied with carrier frequency from an oscillator 2, through a switch 3. This carrier may be modulated in the transmitter by voice currents emanating from the telephone instrument 4 or by tone current from the oscillator 5the tone being emitted in pulses determined by the operation of the code sender shown in the box 31.

When switch 3 is closed, carrier passes from the output of the transmitter to the transmitting medium which may be free space, as in radio, or may be some form of guiding agency, for exam- 10 ple, a pair of wires, as in carrier transmission, or a coaxial conductor system. At the receivers of the controlled stations, of which but one is illustrated in Fig. 1, the incoming signals pass through the high-frequency amplifier 1. Across 15 the output of this amplifier is bridged the tuned. transformer 8 which selects the carrier frequency, which is thereupon rectified to unidirectional current by the rectie 9 and operates the relay I0. Operating the uppery contact of this relay 20 causes a short circuit through contacts I1 across the input terminals of the telephone receiver 20. Operating the lower contact of relay ill connects battery I3 through contact 6 of relay Il to busy signal lamp l5 and thence by ground return back 25 to battery I3, thereby lighting the busy signal and advising the operator that the control station is transmitting. At the same time the relay I6, in parallel with the signal lamp, is operated, whereby the relay contacts, which are in series 30 with a transmitter control circuit, are operated and the transmitter rendered inoperative. This control circuit maybe of any desired type, for. example, it may be the power supply circuit. It is evident then that whenever the carrier from 35 the control station is sent out by the closing of switch 3, all stations within its jurisdiction are thereby rendered inoperative for both transmitting and receiving of messages.

To release-one of these stations for communi- 40 cation and to call its operator is the function of p the code sender 31, the selector 38, and the apparatus operated thereby as will be described. 'I'he code sender 31 and selector 38 are identical with those illustrated in Figs. 1 and 2, respec- 45 tively, of Patent 1,464,565 to Espenschied et al., and function in identically the same manner. Since a detailed understanding of the operation of this apparatus is not essential to' an understanding of the present invention, reference is made to the above mentioned patent for a complete description.

In the code sender disc, TS is toothed in accordance with a code. When rotated it operates contacts 26 and 21 and thereby, through relays 22, 55

23, and 24, as described Vin the patent referred to, causes the contacts of relay 2| to open and close in accordance with the code represented on the toothed disc. Such operation of these contacts permits pulses of voice-frequencyA tone current from oscillator 5 to enter the transmitter I and betransmitted from its output as modulation of the carrier. The code sent from a particular disc is characteristic -oi! a particular station detector I2 and as voice-frequency pulses passes through the transformer 38 which may be any desired known type such, for example, as a transformer tuned to select the tone frequency. Rectifled by rectifier 40 to pulsating direct current.

the code signals pass into the selector 38; through low-pass filter BF; they operate relay R3 and, as described in above mentioned Espenschied patent, act to turn selector wheel RS until contacts 34 and 35 come together, thereby closing the circuit from battery 4I through call bell I8 and the operating winding of relay I4. After this contact interval' the selector wheel falls back to its wait- Y ing position ready to respond again if code wheel TS is again operated. 'I'he selector 38 is so arranged that contacts 34 and 35 will close only when the code peculiar to that selector is received. Thus bell I8 and relay I4 .are not operated vat other stations than. the called station.

Operation of relay I4 opens upper contacts I1 removing the short circuit which had been caused by operation of relay I0 as described above, thereby permitting the receiving of messages in the telephone receiver 20. Operation of relay I4 also opens contacts 6 which cuts off signal lamp I5 and releases relay I6, thereby permitting operation of the transmitter 42 so that it may be used for sending messages. Current ows from battery I3 through lower contact of relay I0 and thence through contact I I, closed by operation of relay I4, to the winding I9, thereby locking the relay I4 in closed position. When selector wheel RS falls back, opening contacts 34 and 35, bell I8 ceases to ring but relay I4 remains operated by virtue of winding I3 as explained above. Communication, both transmitting and receiving,

1 may now be carried on at the station or stations whose code signal has been emitted by the control station, as long as the carrier is present. If the carrier is shut off by opening switch 3, the relay I0 stores which in turn causes relay I4 to restore a the called stations go back to their original condition. Other stations not called are also restored to normal waiting condition by the release of relay Ill since thereby battery is removed from lamp I5 and relay I6.

If it is desired to originate a call from a controlled station, the following procedure takes place. 'I'he operator at the controlled station waits, if necessary, until his busy lamp I5 is extinguished, indicating that the control station is idle. He then operates his transmitter 42 and calls the control station through its receiver 36 either by code calling or by voice, depending on vorder to answer the call the control station operator must lclose his switch 3, which permits carrier to go out, thereby rendering' the, calling station inoperative, as above described. The -control station operator has, however, by listening or through the agency of a code receiver if this be provided, been advised of the designation of the calling station and he sends the code signalfor it,'therebyres'toring it to operative condition but holding silenced all other stations as described above.

If the called station operator does not answer, the called station may be restoredv to normal waiting condition by opening switch-3 which permits relay I 0 to release, thereby unlocking and restoring relay I4.

Fig. 2 shows an arrangement vwhereby the principles of this invention may be applied, utilizing only code signals for the control functions. In fact this form oi' invention may be utilized in a system wherein the single sideband carrier suppression type of transmission is employed.

'I'he high-,frequency transmitter 43 with vits control circuit, closed by switch 48, the` transmitting medium and the high-frequency receiver 44 furnish a means of any desired known kind whereby voice-frequency signals may be transported to a distant station. Code pulses originating from the oscillator 5,y through the senders 31a., 31h, and 31e may be sent as in the case of Fig. l

already described. Each of the three code send-- ers is identical with sender 31 of Fig. 1, but the three have different code discs sending different codes.

At each receiving station arethree code selectors 38a, 38h, and 38c, each identical with code selector 38 of Fig. 1 except as follows: All selectors 38c are responsive only to code sender 31e. Likewise, all selectors 38h are responsive only to code senders 31h. vCode selector 38a is individual to each station in that no two will operate on the same code signal except as may be'required for selective group calling in which it is desired to call several stations with the vsame code. While but one sender 31a is illustrated, it will be understood that one will be required for each station or group to be called to the exclusion of others. As in Fig. 1,` code pulses of tone are transmitted to the receiver, rectied by rectifler 40 and impressed upon the inputs of the code selectors, in this case there being lthree in parallel. 'I'he output contacts of these selectors are connected on one side in parallel through battery 4l to ground and on the other side individually to other apparatus as will now be described.

Let it be assumed that the station on the left desires to call the particularstation illustrated at the right.' Sender 31o is ilrst operated. In response to the code thus sent the contacts of selector 38c are closed and battery 4I thereby connected to the operatingwinding oi' relay 45.

Closure of Vthis relay permits current from battery 41 to flow through locking winding 46, over contacts of relays 45 and 16, and via relays 11, 18, and 19 to ground. 'I'hus relay 45 remains operated when selector 38c drops back to itswaiting position. Relay 11 being operated by current from battery 41, opens the circuit to telephone receiver 28 thus disabling forreceiving messages. Operation oi' relay 18 causes the lighting of busy signal lamp I5 and operation of relay 13 disables the transmitter 42 by opening its control circuit,

which may, for instance, be the power supplycircuit. All controlled stations are now unable to transmit or receive.

Sender'31a is now operated to call a particular station, causing operation of selector 88a at that station. 'I'his connects battery 4I to call bell I8, causing it t ring, and to relay 80, the contacts of which being closed connect the battery 4I also to the winding oi relay 16. When relay 16 operates it opens the circuit from battery 41, thereby releasing relays 45, 11, 18, and 18. These releases permit utilization of the transmitter and receiver and put. out the busy lamp. When selector 38a dropsback to waiting position, relay 88 and, in turn, relay 16 drop back also, but relay 45 is now/ open, no current flows from battery 41 and relays 11, 18 and- 19 remain unoperated.

The called station is now able to communicate with the calling station; meanwhile all other stations remain disabled since their selectors- 38a were not responsive to the code call sent to the called station.

When the communication is nished, sender 31h is operated, thereby operating selectors 38h at all stations. This connects battery 4I to relay 16 whose operation produces results already detailed above. All stations are thus restored to waiting condition.

An operator at a secondary station desiring to originate a call waits until the channel 'is free as indicated by the extinguishment of his busy signal I5, whereupon he operates his transmitter 42 to call the control station. When the control station answers, communication may proceed between the two stations if'desired without any operation of senders or selectors, provided it is not desired to exclude other secondary stations from listening to or interrupting the conversation. If it be desired to exclude others this may be accomplished by operating senders 31e and 31a, as described above for calling a particular station, the particular station to be signaled being in this case the station originating the call.

It willbe evident that, since operationof signaling and lockout features is in no way dependent upon the continuity or presence of the carrier, this system is applicable to a wide variety of types of transmission.

In the arrangement just described the code signals, while modulated as a voice-frequency tone on a carrier, may, in the case of single sideband transmission with carrier suppression, appear in the transmission medium as pulses of a single frequency. The signal is the same as it would be if a carrier itself had been keyed or modulated directly by the code sender and sent. Fig. 3 illustrates a system in which certain features ofthe systems of Figs. 1 and 2 are combined and the code signals are sent as interruptions of the carrier itself.

In Fig. 3 the transmitter I, carrier oscillator 2 and switch 3 arev the same as the corresponding elements in Fig. 1'. In fact many other elements have similar correspondence and similar numbering. In series with key 3 are the contacts of relay 82 whose Winding is connected through the contacts of code sender 31 to battery 83. .Closing of the sender contacts will cause opening of the contacts of relay 82. i

At the receiving end signalsv received through amplifier 1 pass through detector-amplier I2 to telephone receiver 20 unless prevented by short circuit through contacts I1 and the upper contacts of relay 85. Received carrier passing through tuned transformer 8 and rectier 8 operates relay 85. 'Ihrough the lower back contact 8| of this relay current from battery I8 may be caused to ilow to the input of code receiver 88. In other respects the apparatus illustrated is the same as in Fig. 1 and its operation will now be described.

Tovcall a station'among a controlled group the operator of the control station closes his switch 3 which causes carrier to be transmitted continuously from yhigh-frequency transmitter I.. This carrier received through amplier I1 at controlled stationscauses operation oi relay 85 as .just described. Closure of the upper contacts of relay 85 completes a short circuit through contacts I1 across telephone receiver 28 thus preventing receipt of messages. Closure of contact 84 of relay 85 connects battery I3 through contacts 6 of relay I4 to busy signal lamp I5 and relay I6 which, being operated thereby, opens the transmitter control circuit and disables 'transxnitter 42. Thus by closure of switch 8 all stations or transmitting messages. Opening of contacts 8I removes battery I 8 from connection to the codesignal receiver 38 which is then in a position to receive code signal pulses.

Now let the code sender 31 be operated to call a particular station. Closure of the contacts of the sender connects battery 83 to relay 82 which in turn opens the circuit from carrier oscillator 2 to transmitter I. 'I'he pulses of the code signal are thus sent as interruptions or gaps in the carrier. 'I'hese gaps in the carrier allow relay 85 at controlled stations to restore momentarily for each gap, making contact 8| and sending a pulse of direct current from battery I3 into code receiver 38. The selector responsive to the particular code signal sent from sender 31 has its contacts closed to connect battery 4I to relay I4 and to call bell I8. As soon as the sender key has ceased to send pulses its contacts remain open and relay-82 remains unoperated. In this condition continuous carrier isagain sent out f rom transmitter I and allstations except the particular one called are held in a disabled state. The operation of relay I4 at the called station in` combination with the reclosing and holding of relay 85 by the continued presence of steady carrier results in the same sequence of operations as has already been detailed in the descriptionof Fig. 1, viz., ,contact 6 is broken, lamp I5 extinguished and relay I6 released. Contact II is made, putting batter-y I3 on locking winding I9. Contact I1 is opened, releasing telephone receiver 20 for receiving messages. When the code receiver 38 restores itself after a fewmo'ments, bell I8 ceases to ring but relay I4 remains locked and the station may communicate with the control station.

All stations are restored to waiting condition by opening of switch 3 which releases relays 85. Originating a. call from'a control station is done as with the apparatus of-Fig. 1. That is, the controlled station operator calls with transmitter 42 .(not shown), gives thedesgnation of his station and states his desire to call. Then the control station operatorA silences all stations by closing switch 3 and calls the petitioning station by the proper code to release it as described.

In the above detailed description of this invention it has been assumed for the sake of simplicity that but a single master station is equipped for control. It will be evident from the following that the invention need notl be limited in any such way but is applicable to each of a number of stations in an intercommunicating group to the end that any one may' control all `the others. Referring to Fig. 4, for simplicity but two stationsv of an unlimited group are shown.V In each station the transmitters 15 may be like those shown in the dotted enclosure'15 in Fig. 2, while the receivers 14 may belike corresponding receiver shown in dotted enclosure 14 in Ii'ig.y 2. A transmitter control circuit between them is shown by the lines C. C. In Fig. 4 it is assumed that communication between stations is all on one frequency, the antenn 1| being switched in a well-known manner from the transmitter output to the receiver'input by relay 12 in response to the operation of switch 1l by the operator. The normal rest or waiting position of the relay 12 connects the receiver to the antenna.

When all stations in the group are quiescent or` waiting, any one may originate a call to any other in the following manner. The calling station operator closes vhis switch 13 to connect his transmitter to his antenna. Thereupon he may function as a control stationas described above in connection with Fig. 2, and all other stations, remaining in the receiving or waiting condition, become controlled stations. He may call one or more of them having silenced all others as already described. 'I'he intermittent .transmission of carrier resultant from the disconnection of the transmitter from the antenna while receiving does not cause any difficulty because maintenance of the lockout of unwanted stations is not dependent upon the carrier in this form of the invention. When the communication is 1inished and the calling station operator has restored all stations to waiting condition by the procedure already described, the system is free and any other station may originate a call and temporarily become a control station. The use of the control system is in this arrangement entirely optional with the operators. If the control keys are not operated at any station, free intercommunication between any or all stations may b e carried on.

It will be evident from the above that the invention may be appliedto any high-frequency communication system involving a common transmission medium whether radio, wire or one involving a wave guide such, for example, as a concentric conductor system.

It will also be evident that, while the invention has been described above in connection with two-way communication systems, it is not limitedto this use but may be applied to one-way communication systems such as broadcasting systems. For example, if transmitter 42 with its control circuit, and receiver 35 are eliminated from Figs. l, 2, and 3, the illustrations then delineate one-way communication systems in which a central control transmitting station is able to select from time to time vthe receivers which it will permit to listen. Such an arrangement might be employed to deliver different program items to different receiving stations in accordance with a prearranged scheme.

'I'he system is adapted to telegraph transmission simply by replacing telephone transmitter I4 with a suitable form of voice-frequency tone telegraph transmitter and replacing telephone receiver 20 with a corresponding telegraph receiver. These could, for example, be printing telegraph instruments arranged as described in a paper entitled "Application of printing telegraph to long wave radio circuits, by Austin Bailey and T. A.

McCann, published in Vol..X,'pp. (50i-615 of the Bell System Technical Journal. y

It will be disclosed that the general principles herein disclosed may lbe embodied in many other organizations widely different from those illus-v trated without departing from thev spirit of the invention-as defined in the following claims. `What is claimed is:

1. In a carrier current electric Wave signaling system a transmitter, means for controlling the carrier current signals sent out'from said transmitter, said means including a source of selective code signals, a transmission medium, a receiver having in association therewith means responsive to carrier'current from the transmitter to disable the message output of said receiver, and means responsive to selective code signals superposed on said carrier current to re-'enable said output. f

2. An electric wave transmitter and associated therewith a controllable source of carrier frequency and a code signal transmitter, a transmitting medium, and electric wave receiver having associated therewith means responsive to receipt of said carrier frequency to disable an output of said receiver, a code signal selector and means responsive thereto to re-enable said receiver output.

3. An electric wave transmitter, associated therewith a plurality of code senders, a transmitting medium, an electric wave receiver, associated therewith'a first code selector and means responsive thereto to disable the message output of said receiver, a second code selector and means responsive thereto to re-enable the output of said receiver.

4. A carrier current electric wave transmitter, associated therewith means for controlling carrier current signals sent out from said transmitter said means including a source of selective code signals, a, transmitting medium, a plurality of electric wave receivers and in association therewith means responsive to carrier current from the transmitter to disable the message outputs of all receivers and at each station means responsive to selective code signals superposed on said carrier current to re-enable the output of the associated receiver. a

5. An electric wave transmitter, associated therewith a controllable source of carrier frequency and code signal transmitting means whereby code signals may be transmitted as modulations of the carrier wave, a transmitting medium, a plurality of electric wave receivers adapted to receive said modulated carrier, means associated with said receivers and responsive to the receipt of said carrier frequency to disable the message output of said receivers, associated with each receiver a code selector, and means responsive thereto to re-enable the output of the associated receiver.

6. An electric wave transmitting station adapted to send a carrier frequency and modulated thereon selective code signals characteristic of any receiving station, a transmitting medium, a plurality of receiving stations including at each a code selector adapted to receive a particular selective code signal from said transmitting station, means at each receiving station responsive to the carrier signal to suppress the message output of the station and means responsive to said code selector to release saidV output.

7. An electric Wave communication station comprising a transmitter and associated therewith means for supplying selective code signals to the input of said transmitter, a receiver and associated therewith code signal receiving means, means responsive to received signals to disable said transmitter and means actuated by said code signal receiving means to re-enable said transmitter. y

8. In ahigh-frequency signaling and control system, a high frequency transmitters, eans for controlling the signals sent out fromt` Alflie transmitter, said means including a source of selective code signals, a transmission medium, a receiver and in association therewith a transmitter, means responsive to signals from the first mentioned transmitter to disable said second men-i tioned transmitter and the message output, of said receiver and means responsive to selective code signals to re-enable said second mentioned transmitter and said receiver output.

9. In a high-frequency signaling and control system, a high-frequency transmitter, 'means for applying a carrier frequency thereto, means, for modulating said carrier with code signals, a transmitting medium, a receiver and associated therewith a transmitter, means responsive to the presence of received carrier to disable said second mentioned transmitter and the message output of said receiver, selective code signal receiving means responsive to certain of said'code signals to enable said receiver output and said second mentioned transmitter.

10. In a signaling and control lsystem a source of carrier, means for .generating selective code signals, means for modulating said carrier by said signals, means for transmitting said modulated carrier, a receiver and a transmitter associated therewith, means responsive to the unmodulated carrier component to disable said second mentioned transmitter and an outputof said receiver, a selective code signal receiver and means responsive thereto to re-enable said disabled transmitter and said receiver output.

11. A transmitter capable of sending carrier,

a transmission medium, a second transmitter andv associated therewith a receiver for receiving said carrier, means responsive to the receipt of said carrier to disable said second transmitter and the message output of said receiver and means to re-enable said second transmitter and the message output of said receiver.

12. A plurality of stations adapted to intercommunicate by electric Waves, each comprising an electric wave transmitter and an electric wave receiver, means associated witheach transmitter to` send therethrough selective'code signals, a transmitting medium, means associated with each receiver to receive and utilize selective code signals, said means-comprising a first selector and responsive thereto means for suppressing the output of the associated receiver and disabling the associated transmitter, a second selector and responsive thereto means torrelease said output and re-enable said receiver, a third selector and means responsive thereto to operate a call signal and to release said receiver and re-enable said transmitter.

13. A plurality of stations adapted to intercommunicate by electric waves each station including a transmitter and a receiver, means associated with each transmitter to send code signals, a transmitting medium, code selector means at all receiving stations adapted to operate in response to a common code signal, and means responsive thereto to disable all transmitters and the message receiving portion of all receivers, code selector means at each station adapted to operate in response to a code signal characteristic of that station and responsive thereto means to re-enable the associated transmitter and receiver, code selector means at all stations adapted to operate in response to another common code signal, and means responsive thereto toenable all transmitters and receivers.

RALPH BOWN. 

